The invention relates to an influencing device for influencing an active chassis system of a vehicle, the active chassis comprising a plurality of controllable spring or damper units of the vehicle, comprising a roadway sensor which produces sensor data relating to a roadway which is located in front of the vehicle in the direction of travel, said sensor data being used to acquire a roadway profile, wherein a pilot control unit determines, as a function of the acquired roadway profile, a pilot control variable which is used to adapt the setting of the spring or damper units to the acquired roadway profile.
U.S. Pat. No. 6,233,510 B1 discloses a method and a device for determining the state of a roadway and influencing the spring units of the vehicle as a function of the determined state of the roadway. A sensor—for example laser sensor or an image detection sensor—senses the surface of the roadway in front of the vehicle and transmits the sensor data to a control unit which determines the profile of the roadway located in front of the vehicle in the direction of travel. An active chassis system comprising a plurality of spring or damper units is actuated by the control unit as a function of this roadway profile, and performs open-loop or closed-loop control on the spring rate, the damping rate, the pressure, the level etc.
Exemplary embodiments of the present invention provide an influencing device for influencing an active chassis system of a vehicle that improves driving comfort for the vehicle occupants.
The influencing device has a roadway sensor which produces sensor data relating to a roadway located in front of the vehicle in the direction of travel, from which data it is possible to determine a roadway profile which is transmitted to a pilot control unit. The pilot control unit determines, as a function of the roadway profile, a pilot control variable which is used to adapt the setting of the spring or damper units to the acquired roadway profile. On the basis of the pilot control variable, an input variable is for this purpose calculated for a vehicle body control system which is used to perform z control of the position of the vehicle body. For example, the input variable which is acquired using the pilot control variable for the vehicle body control system can modify a setpoint value which is predefined in the vehicle body control system, and as a result can bring about the setting of the active chassis system or of the vehicle to the previously determined roadway profile. The actuation of the spring or damper units as a function of the roadway profile is consequently integrated into a vehicle body control system for controlling the position of the vehicle body.
This ensures that outside the effective range of the pilot controller or when the pilot controller is defective sufficient driving comfort is always ensured, and in such cases the position or the movement of the vehicle body is still controlled using the vehicle body control system. The vehicle body control system which is superimposed on the pilot controller therefore ensures very good driving comfort even when there are faults in the pilot controller.
The pilot control unit advantageously determines a plurality of separate pilot control variables, in particular a pilot control level for each spring or damper unit which is used to acquire a setpoint level of the respective spring or damper unit, and a pilot controller vehicle body position which is used to influence a vehicle body position controller of the vehicle body control system. As a result of this measure, a plurality of degrees of freedom are available for the modification of the vehicle body control system, with the result that the vehicle body control system can very easily be adapted to predefinable conditions or parameters, such as for example the frequency of the roadway excitations which are known by virtue of the acquired roadway profile and which act on the vehicle. The pilot control level can be determined separately for each vehicle wheel here.
In this context, at least the pilot control level can be converted, in a modification stage into a modified pilot control level taking into account predefined properties of the vehicle body control system, and can be used to determine the setpoint level for the spring or damper units. In this way, it is possible to adapt the pilot control level to the system limits or dynamic properties of the vehicle body control system. In particular, the modification stage is embodied as a system dynamics stage, and it determines a dynamics-optimized pilot control level from the pilot control level, wherein the dynamics-optimized pilot control level takes into account the dynamic behavior of the active chassis system of the vehicle.
It is also advantageous if the setpoint level for a spring or damping unit is determined on the basis of the pilot control level and/or a modified pilot control level which is formed therefrom, as well as an output variable of the vehicle body position controller. As a result, simple adaptation of the setpoint level to the acquired roadway profile which is located in front of the vehicle is possible.
Since the pilot control vehicle body position is used to correct an actual state value, fed back to the vehicle body position controller, of the vehicle, improved interaction between the vehicle body control system and the pilot controller can be achieved. In particular, in this context instead of the actual vehicle body position, a vehicle body position which is corrected using the pilot control vehicle body position can be fed to the vehicle body position controller, and/or instead of the actual vehicle body vertical speed can be a vehicle body vertical speed which is corrected using the derivative of the pilot control vehicle body position over time can be fed to the vehicle body position controller. Consequently, it is ensured that the vehicle body position controller does not try to compensate the change in the position of the vehicle body which is possibly brought about by the pilot controller.
The vehicle body control system can have a chassis controller which in turn has the active chassis system with the adjustable spring or damper units which can each contain an adjustable spring and/or an adjustable damper. A pilot control level which is used to influence the actual level of the adjustable spring is determined if an adjustable spring is provided in the spring or damper unit. A damping variable which is used to influence the damping effect of the adjustable damper is determined if an adjustable damper is provided in the spring or damper unit. Consequently, the pilot controller can be integrated into the vehicle body control system comprising an active chassis which has adjustable springs or adjustable dampers or even both.
It is also advantageous if a calculated wheel position which is transmitted to the pilot control unit as an input variable is acquired from the acquired roadway profile in a wheel movement acquisition stage. In this context, in particular the dynamic properties of the vehicle wheel can be taken into account. The pilot control is more precise as a result of the calculated wheel position being taken into account, which further increases the achieved comfort. At least one of the pilot control variables can be acquired as a function of the calculated wheel position.
It is also advantageous if a contour profile describing a position path from a plurality of vehicle body positions for the travel of the vehicle along the roadway profile is acquired on the basis of a variable which describes the roadway profile, wherein the curvature of the contour profile is minimized under the peripheral condition that the maximum spring travel values available at the spring or damper units are complied with. This ensures the greatest possible degree of comfort while taking into account the fact that, depending on the roadway profile, it is not always possible to compensate for all the elevations or depressions in the roadway using the active chassis systems without an effect on the position of the vehicle body.
It is possible for the vehicle body control system to be influenced by the pilot control variable or modified pilot control variable in such a way that the position of the vehicle body when there are roadway excitations in a lower frequency range below a lower cutoff frequency essentially follows the roadway profile. In this lower frequency range, changes in the roadway profile are converted into corresponding changes in position of the vehicle body, which permits a simple implementation possibility for optimizing the comfort while allowing for the system limits.
The lower cutoff frequency may be variable in this context and may depend on a variable which describes the roadway profile, in particular on the acquired, conditioned roadway profile. In addition, the lower cutoff frequency can depend on the maximum spring travel values which are respectively available at the spring or damper units. Since the lower cutoff frequency is minimized under the peripheral condition that the maximum spring travel values available at the spring or damper units are maintained when traveling along the roadway profile which is located in front of the vehicle, it is easily possible to achieve the greatest possible level of comfort while allowing for the system limits, in particular the spring travel limits. The curvature of the contour profile can be minimized very easily while complying with the maximum spring travel values available at the spring or damper units.
In this context, the vehicle body control system can control the position of the vehicle body when there are roadway excitations with frequencies above the lower cutoff frequency with the objective of maintaining the position of the vehicle body essentially unchanged so that a high level of comfort is provided in the region of frequencies above the lower frequency range. In this frequency range, roadway excitations are not to act on the position of the vehicle body. This applies up to an upper cutoff frequency of approximately 8-10 Hz which corresponds to the dynamic limit of the active chassis system.
It is also advantageous to provide a diagnostic unit which acquires a deviation between the anticipated state of the vehicle and the actual, current state of the vehicle on the basis of a variable which describes the roadway profile and a variable which describes the current state of the vehicle. In this way, control errors or else system defects can be detected.
The diagnostic unit acquires the anticipated state of the vehicle on, for example, the basis of the acquired roadway profile, in particular using a predefined vehicle model.
It is also possible for the diagnostic unit to acquire, on the basis of the deviation, a correction value which is used to adapt the pilot control variable and/or the modified pilot control variable. As a result of this configuration it is possible, at least partially, to adapt the influencing device to external conditions and compensate, for example, wear states of the active chassis system or changed dynamics of the vehicle body control system due to temperature fluctuations.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.